A complete narrowed housing with a backbraced tube, a good set of 31 or 35 spline axles, nodular center section like a Currie or Strange and a Detroit locker or a full spool will set you back anywhere from $1500.00 to $2500.00. To tub the car with relocating hard points and adding ladder bars, depending on of course who does it could run from $800.00 to $1500.00.
Figure that the entire job, including wheels and tires will set you back about $5000.00.
A mini tub is a bit less, but the ladder bars or 4 link require a crossover to connect the front, so they also have to install tubular sub-frames with crossovers to tie them down. Go check out
http://www.cachassisworks.com/ and click on the "how to" and then click on "installing a subframe and suspension". They are the same company who did mine, and it's a real education...and it's on a 66 Mustang.
Ron